1. Field of the Invention
The present invention relates to a method of manufacturing an electronic device, particularly, to a method of manufacturing an electronic device in which the process step after the reactive ion etching (RIE) treatment is improved in the manufacture of a semiconductor device or a liquid crystal display device.
2. Description of the Related Art
In, for example, a semiconductor device, aluminum or copper is used for forming the metal wiring. A so-called “electromigration”, in which migration of aluminum atoms is brought about by the current applied to a device, is generated in the aluminum wiring. An aluminum alloy containing a small amount of copper is used for forming a wiring effective for preventing the electromigration.
Also, an aluminum alloy prepared by adding a small amount of silicon or titanium to aluminum is used for forming the wiring in order to minimize the generation of an electric spike in the contact hole.
The metal wiring included in the semiconductor device is formed by the various processes given below:
1) In the first step, a metal layer containing aluminum is formed on an insulating film on a semiconductor substrate. Then, the metal film is covered with a resist film, followed by subjecting the resist film to a so-called “photographic etching”, in which the resist film is subjected to the exposure to light and the developing treatment, so as to form a resist pattern. Further, the exposed portion of the metal layer is selectively removed by a reactive ion etching (RIE) treatment with the resist pattern used as a mask so as to form a wiring containing aluminum. Finally, the residual resist pattern is peeled off and removed.
After formation of the metal wiring by the selective etching of the metal layer containing aluminum and formed by method 1) given above by means of a RIE treatment using a resist pattern, a residue derived from the metal and the resist such as a polymer and a denatured layer is attached to the surface and the side wall of the metal wiring. The particular residue lowers the reliability of the semiconductor device. Such being the situation, it was customary in the past to treat the formed metal wiring with an alkali aqueous solution such as an aqueous solution of hydroxylamine so as to remove the residue.
However, since the wiring contains an amphoteric aluminum, the wiring is etched within an alkali aqueous solution such as an aqueous solution of hydroxylamine so as to be thinned, with the result that the resistance value of the wiring is increased.
2) In the first step, a metal layer containing aluminum is formed on a first layer insulating film on a semiconductor substrate, followed by covering the metal layer with a resist film and subsequently subjecting the resist film to a photographic etching so as to form a resist pattern. Then, the exposed portion of the metal layer is selectively removed by a RIE treatment with the resist pattern used as a mask so as to form a first layer wiring. After formation of the first layer wiring, the resist pattern is peeled off and removed, followed by forming a second layer insulating film on the first layer insulating film including the first layer wiring. Then, a resist film is formed on the second layer insulating film, followed by applying a photographic etching to the resist film so as to form a resist pattern having openings formed in the portions where via holes are to be formed. Further, the exposed portions of the second layer insulating film are selectively removed by a RIE treatment with the resist pattern used as a mask so as to form via holes. Still further, a conductive barrier film and a metal film such as a tungsten film are deposited on the second layer insulating film including the via holes so as to form a conductive barrier film on at least the inner surface of the via hole. At the same time, the via hole having the conductive barrier film formed on the inner surface is filled with the metal film. Then, a chemical mechanical polishing (CMP) treatment is applied to the metal film and the conductive barrier film so as to form a via fill connected to the first layer wiring in the second layer insulating film.
In the next step, a metal layer is formed to cover the second insulating film including the via fill, followed by covering the metal layer with a resist film. The resist film thus formed is subjected to a photographic etching so as to form a resist pattern. Then, the exposed portion of the metal layer is selectively removed by a reactive ion etching (RIE) treatment with the resist pattern used as a mask so as to form a second layer wiring.
After formation of the via hole by selectively etching the second layer insulating film formed by method 2) described above by means of the RIE treatment using the resist pattern, a residue such as a polymer derived from the resist and the denatured layer derived from the resist and the material of the insulating film is attached to the inner surface of the via hole. If a conductive barrier film is formed on the inner surface of the via hole with the residue left unremoved, the conductive barrier film is peeled off in the subsequent step of burying a metal film in the via hole, with the result that the barrier function is impaired. Such being the situation, it was customary in the past to treat the inner surface of the via hole with an alkali aqueous solution such as an aqueous solution of hydroxylamine so as to remove the residue.
However, the first layer wiring exposed to the outside from the bottom portion of the via hole contains an amphoteric aluminum and, thus, is etched within an alkaline aqueous solution such as an aqueous solution of hydroxylamine. As a result, the thickness of, for example, the first layer wiring is decreased so as to increase the resistance value of the first layer wiring. In an extreme case, a serious problem is generated such that the first layer wiring is caused to disappear or is broken.
Also, after formation of the second layer wiring by selectively etching the second metal layer formed by method 2) described above by means of a RIE treatment using a resist pattern, a residue such as a polymer or a denatured layer derived from the metal and the resist is attached to the surface and the side wall of the second layer wiring. What should be noted is that the particular residue lowers the reliability of the semiconductor device. Such being the situation, it was customary in the past to treat the surface of the second layer wiring with an alkali aqueous solution such as an aqueous solution of hydroxylamine after formation of the second layer wiring so as to remove the residue.
However, if the width of the second layer wiring is made smaller with progress in the degree of integration of the semiconductor device, the via fill is not covered with the second layer wiring in the contact portion with the second layer wiring so as to be exposed to the outside. Therefore, where the via fill is formed of a material containing tungsten as a main component, a serious problem is generated that, when the second layer wiring is treated with an alkali aqueous solution such as an aqueous solution of hydroxylamine, the alkali aqueous solution is also brought into contact with the via fill formed of a material containing tungsten (W) as a main component. The dissolution of tungsten is derived from a large difference in the ionization tendency (potential difference) between the second layer wiring, e.g., Al, and tungsten in the presence of the alkali aqueous solution in mainly the contact portion noted above.
Jpn. Pat. KOKAI Publication No. 2001-247986 discloses a composition for removing smut comprising an oxidizing agent such as ammonium peroxodisulfate, an acid such as sulfuric acid or phosphoric acid, and a halide ion-containing compound such as hydrofluoric acid. It is taught that a part or an article made of aluminum or an aluminum alloy is treated with the particular composition before application of an electroplating treatment to the part or the article made of aluminum or an aluminum alloy so as to remove the metal and the oxide (smut) inhibiting the electroplating process from the particular part or the article.
An object of the present invention is to provide a method of manufacturing an electronic device, which involves formation of a wiring made of aluminum or an aluminum alloy by a reactive ion etching (RIE) treatment and which permits removing the metal residue attached to the surface and the side wall of the wiring and the polymer and the denatured layer derived from the resist in the treatment after formation of the wiring without bringing about, for example, the thinning of the wiring by the etching.
Another object of the present invention is to provide a method of manufacturing an electronic device, which involves formation of a via hole for a via fill in an insulating film for an electrical connection to the underlying wiring made of aluminum or an aluminum alloy by a RIE treatment and which permits removing the polymer and the denatured layer derived from the resist attached to the inner surface of the via hole in the treatment after formation of the via hole in the insulating film without bringing about, for example, the thinning of the underlying wiring by the etching.
Further, still another object of the present invention is to provide a method of manufacturing an electronic device, which involves formation of a fine wiring by a RIE treatment in an insulating film having a tungsten-based via fill formed therein such that the fine wiring is exposed to the outside in the contact portion with the via fill and which permits removing the metal residue attached to the surface and the side wall of the wiring and the polymer and the denatured layer derived from the resist in the treatment after formation of the fine wiring without bringing about the dissolution of tungsten contained in the exposed portion of the via fill.